Deduplicating storage with improved recognition of common blocks

Detecting a duplication of data comprises managing a fingerprint directory that contains one or more entries, each entry contains a data and a fingerprint data storage location for a data block. Each entry is assigned a sight-counted attribute, which is an indication of how often the fingerprint has been seen in incoming data blocks. Entries with higher frequency in the directory will be maintained, and the timeliness of data access is considered. A duplicate detector detects that the data fingerprint for a new block is the same as the fingerprint data that is included in an entry in the fingerprint list.